A Park Avenue apartment is a Park Avenue apartment, but when people brag, dote and obsess on the idea of a Park Avenue rental apartment, they're generally not talking about the comparatively modest stretch of Park Avenue south of Grand Central Station. Long considered a poor relative of the “real” Park Avenue of the Upper East Side, Park Avenue South has lately stepped out as an address worth attention in its own right -- both because apartments for rent on Park Avenue South offer solid value per square foot, and has lately come into its own as a place to live and socialize. Convenient, walkable and steadily breaking its associations with unromantic Midtown East, the rental listings of Park Avenue South are finally getting their due.